Method for physical random number generation using a vertical cavity surface emitting laser

Abstract

A method for physical random number generation includes the steps of: modulating the gain of a vertical-cavity surface-emitting laser periodically from the lower threshold to the upper threshold and back; maintaining the gain per round trip positive for a longer period than the round trip time of the cavity; maintaining the net gain per round trip negative for a longer period than the round trip time of the cavity, in order to create optical pulses of random amplitude; detecting the optical pulses; converting the optical pulses into electrical analog pulses; and digitising the electrical analog pulses into random numbers.

1 . A method comprising:
 modulating a gain of a vertical-cavity surface-emitting laser periodically from below a regime of spontaneous emission to above a regime of stimulated emission to create optical pulses of random amplitude;   detecting, before the optical pulses reaches a maximum value, the optical pulses;   converting the optical pulses into electrical analog pulses; and   digitizing the electrical analog pulses into random numbers.   
     
     
         2 . The method of  claim 1 , wherein detecting the optical pulses comprises detecting the optical pulses via a fast photodiode. 
     
     
         3 . The method of  claim 1 , wherein modultating the gain comprises setting a biasing current point of the vertical-cavity surface-emitting laser below a threshold level and adding an additional modulating current. 
     
     
         4 . The method of  claim 3 , wherein the additional modulating current varies between −2 mA and +2 mA. 
     
     
         5 . The method of  claim 1 , wherein digitizing the electrical analog pulses comprises digitizing the electrical analog pulses via an 8-bit digitizer or a comparator. 
     
     
         6 . The method of  claim 5 , wherein the comparator operates as a 1-bit resolution digitizer. 
     
     
         7 . The method of  claim 1 , wherein modulating the gain comprises:
 maintaining gain per round trip positive for a longer period than a round trip time of a cavity of the vertical-cavity surface-emitting laser; and   maintaining net gain per round trip negative for a longer period than the round trip time of the cavity, to create optical pulses of random amplitude.   
     
     
         8 . An apparatus comprising:
 a vertical-cavity surface-emitting laser;   an electric pulse diver configured to modulate a gain of the vertical-cavity surface-emitting laser periodically from below a regime of spontaneous emission to above a regime of stimulated emission to create optical pulses of random amplitude;   an optical detector configured to detect, before the optical pulses reaches a maximum value, the optical pulses and convert the optical pulses into electrical analog pulses; and   a digitizer configured to digitize the electrical analog pulses into random numbers.   
     
     
         9 . The apparatus of  claim 8 , wherein the optical detector comprises a fast photodiode. 
     
     
         10 . The apparatus of  claim 8 , wherein the electric pulse diver is configured to set a biasing current point of the vertical-cavity surface-emitting laser below a threshold level and add an additional modulating current. 
     
     
         11 . The apparatus of  claim 10 , wherein electric pulse diver configured to add the additional modulating current such that the additional modulating current varies between −2 mA and +2 mA. 
     
     
         12 . The apparatus of  claim 8 , wherein the digitizer comprises an 8-bit digitizer or a comparator. 
     
     
         13 . The apparatus of  claim 12 , wherein the comparator comprises a 1-bit resolution digitizer. 
     
     
         14 . The apparatus of  claim 8 , wherein the electric pulse diver configured to modulate the gain of the vertical-cavity surface-emitting laser by:
 maintaining gain per round trip positive for a longer period than a round trip time of a cavity of the vertical-cavity surface-emitting laser, and   maintaining net gain per round trip negative for a longer period than the round trip time of the cavity, to create optical pulses of random amplitude.